rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P9/1:b..l (detected by 0, t=10502 jiffies, g=6441, q=136) task:kworker/u4:0 state:R running task stack:21512 pid: 9 ppid: 2 flags:0x00004000 Workqueue: writeback wb_workfn (flush-8:0) Call Trace: context_switch kernel/sched/core.c:5030 [inline] __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780 irqentry_exit+0x63/0x70 kernel/entry/common.c:432 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676 RIP: 0010:_raw_spin_lock_irqsave+0x24/0xf0 kernel/locking/spinlock.c:161 Code: 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 54 53 48 83 e4 e0 48 83 ec 60 48 89 fb 65 48 8b 04 25 28 00 00 00 48 89 44 24 48 <48> c7 04 24 b3 8a b5 41 48 c7 44 24 08 e7 6a a5 8b 48 c7 44 24 10 RSP: 0018:ffffc90000ce6ca0 EFLAGS: 00000286 RAX: c3bbfa13cdcea700 RBX: ffff888073c44a98 RCX: ffff88813fed0000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888073c44a98 RBP: ffffc90000ce6d30 R08: dffffc0000000000 R09: ffffc90000ce6e20 R10: fffff5200019cdc6 R11: 1ffff9200019cdc4 R12: dffffc0000000000 R13: 1ffff9200019cdb4 R14: ffff888023930000 R15: ffffea0001cae400 __test_set_page_writeback+0x56a/0xe70 mm/page-writeback.c:2851 ext4_bio_write_page+0x293/0x1f90 fs/ext4/page-io.c:-1 mpage_submit_page+0x17a/0x210 fs/ext4/inode.c:2113 mpage_map_and_submit_buffers fs/ext4/inode.c:2361 [inline] mpage_map_and_submit_extent fs/ext4/inode.c:2500 [inline] ext4_writepages+0x1a1f/0x2d20 fs/ext4/inode.c:2829 do_writepages+0x48d/0x6d0 mm/page-writeback.c:2386 __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1647 writeback_sb_inodes+0x9fe/0x1610 fs/fs-writeback.c:1930 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:2001 wb_writeback+0x455/0xb90 fs/fs-writeback.c:2106 wb_check_old_data_flush fs/fs-writeback.c:2206 [inline] wb_do_writeback fs/fs-writeback.c:2259 [inline] wb_workfn+0xaaa/0xe60 fs/fs-writeback.c:2288 process_one_work+0x863/0x1000 kernel/workqueue.c:2310 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 rcu: rcu_preempt kthread starved for 10536 jiffies! g6441 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:27584 pid: 15 ppid: 2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5030 [inline] __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376 schedule+0x11b/0x1e0 kernel/sched/core.c:6459 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 rcu: Stack dump where RCU GP kthread last ran: NMI backtrace for cpu 0 CPU: 0 PID: 4353 Comm: syz.4.30 Not tainted 5.15.182-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 Call Trace: dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106 nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline] rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487 print_other_cpu_stall+0x10c8/0x1220 kernel/rcu/tree_stall.h:592 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline] rcu_pending kernel/rcu/tree.c:3932 [inline] rcu_sched_clock_irq+0x831/0x1110 kernel/rcu/tree.c:2619 update_process_times+0x193/0x200 kernel/time/timer.c:1818 tick_sched_handle kernel/time/tick-sched.c:254 [inline] tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473 __run_hrtimer kernel/time/hrtimer.c:1690 [inline] __hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1754 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1816 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline] __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline] sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676 RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline] RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202 Code: f6 ff 0f 1f 00 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 4e d6 b1 f7 48 89 df e8 16 ab b2 f7 e8 51 4f d3 f7 fb bf 01 00 00 00 46 cf a6 f7 65 8b 05 e7 e2 57 76 85 c0 74 02 5b c3 e8 94 ed 55 RSP: 0018:ffffc9000310fbc0 EFLAGS: 00000282 RAX: ea2cfb3d98369d00 RBX: ffff8880246d65c0 RCX: ea2cfb3d98369d00 RDX: dffffc0000000000 RSI: ffffffff8a0b0fc0 RDI: 0000000000000001 RBP: 0000000000000000 R08: dffffc0000000000 R09: ffffed10048dacb9 R10: ffffed10048dacb9 R11: 1ffff110048dacb8 R12: ffff8880246d65c0 R13: 0000000000000011 R14: dffffc0000000000 R15: 0000000004000000 spin_unlock_irq include/linux/spinlock.h:413 [inline] get_signal+0x11d6/0x12c0 kernel/signal.c:2903 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867 handle_signal_work kernel/entry/common.c:154 [inline] exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline] syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f9828d0a969 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f9826b300e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 00007f9828f32168 RCX: 00007f9828d0a969 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f9828f32168 RBP: 00007f9828f32160 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9828f3216c R13: 0000000000000000 R14: 00007ffcca692fc0 R15: 00007ffcca6930a8